Category: tips

Clever Code

Clever Code

Getting into JS and come across code that many will consider ‘clever’ code. Is this code that is unreadable or is it the features that the language provides? I’m not really going to get into that discussion here – this post will hopefully instead help show and explain what is going on with such code. So should you see it then you’ll be able to understand what is going on and maybe even use it yourself.

const selective = [
    { id: "firstObjectId", ...obj1 },
    { id: "secondObjectId", ...obj2 },
    ...(obj3 ? [{ id: "thirdObjectId", ...obj3 }] : [])
  ];

What’s the aim of this code?

The aim of the above is to inject an ID into every object and at the same time it will only return two items if obj3 does not exist, and 3 if it does.

Why?

You may wish to combine a series of requests and sometimes you expect one of the requests to come back with nothing. If it does then there will be no need to return the 3rd element as an empty object – just drop it.

Explanation

Part 1 – What is { id: “firstObjectId”, …obj1 } doing? It’s taking the values from obj1, spreading them into another object while at the same time including an ID value. So it’s a new object with an ID as well as everything that was inside obj1 to start with.

What about …(obj3 ? [{ id: “thirdObjectId”, …obj3 }] : [])
Well if obj3 exists then it’s the same as the previous lines.
If it doesn’t exist then the line of code is

const selective = […([])]
which is

[…[]]

As the array is empty the spread operator will take nothing out of an empty array which leaves an empty array!
So we combine that with with the other spread objects and we now have a neat means of checking if an object exists and only if it does then include it in a returned item.

Old School

If this were in old school code it would look something like this

const returned = [
{ id: "firstObjectId", ...obj1 },
{ id: "secondObjectId", ...obj2 },
];
if (obj3) {
returned.push({ id: "thirdObjectId", ...obj3 });
}

So you are including an ‘if’ and then pushing the item into the array. Not quite as elegant!

Debugging facebook apps locally (web based ones)

Debugging facebook apps locally (web based ones)

If  you’re wanting to develop a facebook app then there is loads of helpful stuff out there to get you going. Specifically I’d start here if you’re interested http://www.adobe.com/devnet/facebook.html.

But what they don’t tell you is how to debug your app without you having to FTP your files each time you change something. (If your facebook app is based on AIR and not a web app, then this doesn’t matter).

  • Firstly log into facebook and go to your app settings, it will probably look like the below. What you are looking for is the ‘website with facebook login’. This is used by facebook when your app logs in ( you’d never have guess that! ). Anyway if this doesn’t match the url of where your app is deployed then you will NOT be able to log in.

    Change it to your local URL, in my case I’ve made it http://localhost/facebookLoginTest/index.html
    The important bit is the localhost as my actual app isn’t run from index.html but when I set up the app on facebook I just put that in.
  • Now that your app can login you will now be able to debug, but the default settings in Flashbuilder don’t output your files to your localhost. So this is the second part to getting everything to work.

    I’ve highlighted the two bits you need to change which is inside your projects properties (right click and select ‘Flex Build Path’).

    Change the output folder to push your output files to the folder inside your webserver. I use XAMPP to setup my webserver etc

    Also update the output folder URL, once changed when you hit debug it will load whatever URL is in that box + the html page. So as you can see I’ve changed my output folder URL to http://localhost/facebookLoginTest/ which when I run/debug my app gives me http://localhost/facebookLoginTest/FacebookTestApp.html?debug=true

That’s it.

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iOS – Mobile dev, make sure you flush when you’re done.

iOS – Mobile dev, make sure you flush when you’re done.

Developing for Apple’s devices can throw up a few little quirks that don’t happen when using Android devices.

This one happens if you are using shared objects to store information between sessions.
Basically, you should always call the flush mechanism whether you are adding more data to the shared object or if you are deleting something from the shared object.

What you find is if you have a shared object ‘shared’ with a value shared.data.firstValue = “something”, then you delete that value using

delete shared.data.firstValue;

if you try to access the value firstValue you will get null.
This is exactly what I’d expect.

Then lets say you exit the app and you either kill the app from running in the background or iOS stops it. Then the next time you load the app and access the shared object shared.data.firstValue you will get back “something” and not null.

You must flush the shared object for it to be stored locally, otherwise when the app is killed, the local storage will not have been updated.

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Updating bindings when you only change a property inside an Object

Updating bindings when you only change a property inside an Object

Its quite a common thing with Flex and actionscript projects to create an Object and inside that object it will have many properties.  Something in your view will be bound to the object so that the view changes with the object. So long as you change the entire object this will work fine.

Where this doesn’t work is if you change a property inside the object.

So if we have something like this

[Bindable]			
private var myObject : ObjectDataVO;
 
<view:SomeComponent
...
data="{ myObject }"
...
/>

When we set myObject to something the view component gets updated (great so far).
Lets say the myObject has a property text and the view component uses this to display some visual label, then somewhere in the app I change that property, myObject.text = “something else”;
The binding will not trigger as I haven’t actually changed the myObject, just a property inside it.

So how do we fire the binding manually? Well there is the BindingManager class (note this is an excluded class so you’ll not see it in the autocomplete ).
So in this example if I changed the myObject.text property then I could call

BindingManager.executeBindings( this, ‘myObject.text’, myObject );

This would fire of the binding as if the actual myObject had changed so anything listening in will now get updated.

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Additional compiler arguments – debug only code

Additional compiler arguments – debug only code

Many times you look something up, do it once and think cool I’ll remember that as it’s simple. Then 1 year later you’ve forgotten the syntax and you can’t find that help/blog page where you learned about it the first time.
Well I needed to add in some debug code that would only be there for debugging, and the last thing I want to do when building a release version is to scan through the code to remove it. So the ideal way is to use a conditional compiler argument.

So in Flashbuilder, under the project properties and then the Flex compiler properties you’ll see something like this

Compiler Arguments
Example for custom arguments

So if you had the following defined, -define=CONFIG::DEBUG,true -define+=CONFIG::SOMETHING_ELSE,false

Then in code you could do the following.

    CONFIG::DEBUG
    private var test : Boolean;
 
    CONFIG::SOMETHING_ELSE
    private function somethingElse() : void
    {
 
    }

The variable and function code will only be included if the compiler argument is true. So in the above example if you called the function ‘somethingElse()’ then this would generate a build error as somethingElse() doesn’t exist. Change the argument to true and it will build fine.

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Simple tip #4 (GOTCHA) – Datagrid borders

Simple tip #4 (GOTCHA) – Datagrid borders

More of a gotcha than a simple tip.

I was customising a DataGrid with various skin parts the other day (Flex 3) and could I get the borderskin to show, heck no! Its been a while since I had to create a DG from scratch so I’d obviously blacked out any previous pain with using the dammed DG.

Anyway why would the borderskin not show? I tried a simple solid border, nope. I tried a custom png graphic taken from Fireworks for the DG’s border, nope. I tried a programmatic skin border and guess what nope – nothing.  The issue was that I had the background alpha set to 1 (which is pretty normal!) and I had set the alternate row colours.

Setting the background alpha to something less than 1 revealed the border so I ended up fudging it by creating the programmatic skin border by whatever the borderThickness is outside the size of the DG.  
So if the DG was meant to be 400px wide and borderThickness was 2, I made the DG 396px wide and drew the border outside that area.  This is what I’ve expect to happen automatically.

Can’t believe I’ve missed this/forgotten this before. Crappy DG.

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Simple tip #2 – random colours

Simple tip #2 – random colours

Their are so many times I’ve used a random colour in my apps (mainly for testing) that I thought I’d add this way of using a getter method with actionscript to simplify the process.

First of if you haven’t got one already, create a uiltily class so features that you use regulary across projects (you could turn this file into a SWC and reference that in you various projects – now that I think about it I explain this as simple tip #3 🙂 )

So inside your utility class place the following code

public static function get randomColour() : uint {
	return Math.random() * uint.MAX_VALUE;
}

Then lets just say you require a random colour for anything just call Utility.randomColour, no brackets, no = signs. Because you’ve set the function as a getter using the function name will be enough. This method also means that you don’t need to remember the max/min values for a colour. The uint min and max values are the same as the the min/max values for colours.

e.g.

<mx:Canvas backgroundColor="{Utility.randomColour}"
   width="600"
   height="600">

Utility is the name of the class that holds my utility functions.

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Simple tip #3 – Utility SWC (library project)

Simple tip #3 – Utility SWC (library project)

Do you frequently use simple actionscript functions in more than one project. Perhaps you’ve got a function to do tracking, parse strings to dates, or return a random colour etc.

I’m sure most folk will have struggled to think of what project they last used a generic function ABC in as they could do with using it for project XYZ and would rather spend 30 mins searching for said function rather than rewrite it.

Well as explained below is a way to stop this from happening and hopefully save you a heap of time.

  • Step 1

    – Create a library project.

  • So using flexbuilder, go to File->New->Flex Library Project.
  • This will create an empty library project.
  • Step 2

    – add in your Utilty class to the library project.

  • To do this add/create a Utility actionscript file that contains your static functions. Save, and this should then automaticlaly create a SWC file inside the library bin folder. (If it hasn’t and the file added has no errors then check the project properties to make sure the newly added file is being included – see pic)

  • Step 3

    – add the reference of the newly created SWC file to any project you intend to use it in.

  • So go to your project you wish to use the SWC with, then select the projects properties and inside ‘Flex build path’ select ‘Add SWC’.
  • Browse to the the previous library project and select the SWC from its bin folder.

You are now done, any time you update the code in the library project, those changes will be reflected in any project that references the SWC file automatically.

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Simple tip #1 – custom events

Simple tip #1 – custom events

Today while coding I was creating some classes that required them to dispatch custom events. I know that this is a fairly common thing to do but sometimes it is these little things that can trip you up or take a while to find out how to do them.

So I thought that each time I come across something that is ‘simple’ (only simple after you know it!) that I’ll try to create a quick blog entry and take note of it.  Each time I create a new ‘tip’ post I’ll link it to the previous/next tip so that it will be quick and easy to browse through a load of tips.
 

Tip #1

So for my first tip, this is how to implement your own custom events.

First if you are firing the events from a custom MXML file then you need to create a metadata tag. I make this the first node inside the MXML file.  For example:

 

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml"
		width="500"
		height="300"
		>
 
<mx:Metadata>
<!-- 
First two event are plain string events, they do not pass any specific data with them -->
<!-- 
The last event is a custom class that extends Event and as such you need to give
it its package name + the class name as the type -->
	[Event('next')]
	[Event('previous')]
	[Event(name='jump', type='com.kennethsutherland.events.JumpEvent')]
</mx:Metadata>
...

If your custom class is an AS3 file then you would put something like the following are the imports

[Event(name="previous", type="flash.events.Event")]
[Event(name='jump', type='com.kennethsutherland.events.JumpEvent')]

Then inside the MXML file (script block) or anywhere in the AS3 file to fire the event I’d do the following:
 

//custom event, the extra value is handled by the JumpEvent class
dispatchEvent(new JumpEvent("jump", specificValueForTheJumpEventClass));
//standard event
dispatchEvent(new Event("next"));

If you do the above and lets just say your MXML/AS file is called ‘GreatComponent’ then in order to use the new custom event, its as simple as the below bit of code. 

<local:GreatComponent
    next="doSomething()"
    jump="doSomethingElse(event)"
/>

That’s it, now you can fire of any custom event that you wish and make sure that it gets listened to.

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